Wireless-based positioning systems rely on having a number of wireless transmitters. Such “static beacons” have known properties, including position and signal strength. These static beacons act as reference points from which positions of non-static devices can be calculated. It is possible to reduce the power output of the static beacons, which results in lower signal strength and a reduced range of visibility to non-static devices. Maintaining a lowered signal strength reduces the power usage of the static beacons, which in turn reduces the running cost of the system as a whole and achieves the usual environmental benefits of reducing power consumption.
As the density of static beacons increases within a given area, the accuracy of calculation increases. With reference to FIG. 1A, the signal of a static beacon SB1 covers an area SB1A. Area SB1A defines the area in which a non-static device, such as mobile device MD1, may reside and receive wireless signals from a static beacon. Such signals may be used to calculate position information for the mobile device MD1. Adding a second static beacon SB2 that covers area SB2A, shown in FIG. 1B, increases the accuracy for determining the current location of mobile device MD1 because MD1 is in the range covered by both SB1 and SB2. Adding SB2 also increases the total range for MD1. Therefore certain benefits exist for providing a greater number of static beacons within the system.
Due to power and hardware requirements in current implementations, however, rising density equates to rising cost. Furthermore, as density increases the marginal utility of each additional beacon decreases. Referring to FIG. 1C, adding another static beacon SB3 may provide additional accuracy for MD1. However, the additional area of coverage for MD1 achieved by adding SB2 to SB1 is significantly larger than that gained by adding SB3, and thus the benefits of adding SB3 are mitigated by the diminishing returns for the additional area of coverage of SB3. This is particularly true for a presence-based algorithm.
Accordingly, there is a need in the art for a system and method that provides power consumption reduction for wireless beacons without substantially impacting the accuracy calculation.